Is it safe to lager in a 6 gallon plastic better bottle carboy? I know there is always a concern with plastic and oxidation. My lager phase will be 8 weeks at the most.
After the yeast drops out and you are sure there are no off-flavors, you can package (keg or bottle) and lager for however long you want.
If you must lager in the Better Bottle, you can relax because they are made with PET plastic which is somewhat more impervious to oxygen ingress than other plastics, though not as impervious as glass.
I’ve lagered in PET for 4 weeks with no oxidation flavors.